Theoretical aspects of retention in overloaded columns.

Issues regarding the concentration dependent solute distributions in overloaded chromatographic columns are discussed. Geometric simplicity of wall-coated capillary columns is taken as a reference and the discussion is developed using the example of the absorption isotherm of a solute having more affinity for itself than for the stationary phase. A retention function is deduced solving the equation of motion for the peak maximum, making some approximations.

Retention in overloaded columns, an experimental approach.

Employing a micro-bore silica capillary coated with Carbowax 20 M, the dependence of chromatographic retention upon operative variables was studied surpassing the sample capacity of the column. Solution thermodynamics in the non-linear range of the absorption isotherm of n-alkanes on poly(ethylene oxide) were analyzed interpreting the experimental data through a retention equation deduced in a preceding theoretical work. At 120 degrees C, and pressures up to 11 bar abs, deviations from the ideal-gas behavior are found to be negligible, either for the fluid dynamics of the carrier-gas, or the thermodynamics of solution of the n-alkanes.

Application of capillary gas chromatography to studies on solvation thermodynamics.

The potentiality of capillary gas chromatography (GC) as a means for research on solubility phenomena is focused. Basic thermodynamic information can be obtained in a simple and direct way from this technique relying on few parameters with their associated errors tightly controlled. An unexplored field of solvation phenomenology inaccessible to other techniques is revealed by the accuracy of capillary GC, provided that relevant chromatographic variables are utilized and an adequate treatment of the experimental information performed.

Considerations on the temperature dependence of the gas-liquid chromatographic retention.

A discussion on the temperature dependence of the partition coefficient K is developed. This discussion embraces topics such as the limitations of conventional thermodynamic approaches followed in the chromatographic literature, qualitative theoretical notions arising from molecular thermodynamics and the experimental information that is accessible through modern capillary gas chromatography. It is shown that the heat capacity difference of solute transfer for flexible molecules has at least one maximum in the chromatographic range of temperature.